Charting architecture

Decision: one chart engine for all live metrics

Engine: github.com/go-analyze/charts (pure Go, no CGO, SVG output) Theme: grafana (dark background, coloured lines)

All live metrics charts in the web UI are server-side SVG images served by Go and polled by the browser every 2 seconds via <img src="...?t=now">. There is no client-side canvas or JS chart library.

Rule: live charts must be visually uniform

Live charts are a single UI family, not a set of one-off widgets. New charts and changes to existing charts must keep the same rendering model and presentation rules unless there is an explicit architectural decision to diverge.

Default expectations:

same server-side SVG pipeline for all live metrics charts
same refresh behaviour and failure handling in the browser
same canvas size class and card layout
same legend placement policy across charts
same axis, title, and summary conventions
no chart-specific visual exceptions added as a quick fix

Current default for live charts:

legend below the plot area when a chart has 8 series or fewer
legend hidden when a chart has more than 8 series
10 equal Y-axis steps across the chart height
1400 x 360 SVG canvas with legend
1400 x 288 SVG canvas without legend
full-width card rendering in a single-column stack

If one chart needs a different layout or legend behaviour, treat that as a design-level decision affecting the whole chart family, not as a local tweak to just one endpoint.

Why go-analyze/charts

Pure Go, no CGO — builds cleanly inside the live-build container
SVG output — crisp at any display resolution, full-width without pixelation
Grafana theme matches the dark web UI colour scheme
Active fork of the archived wcharczuk/go-chart

SAT stress-test charts

The drawGPUChartSVG function in platform/gpu_metrics.go is a separate self-contained SVG renderer used only for completed SAT run reports (HTML export, burn-in summaries). It is not used for live metrics.

Live metrics chart endpoints

Path	Content
`GET /api/metrics/chart/server.svg`	CPU temp, CPU load %, mem load %, power W, fan RPMs
`GET /api/metrics/chart/gpu/{idx}.svg`	GPU temp °C, load %, mem %, power W

Charts are 1400 × 360 px SVG when the legend is shown, and 1400 × 288 px when the legend is hidden. The page renders them at width: 100% in a single-column layout so they always fill the viewport width.

Ring buffers

Each metric is stored in a 120-sample ring buffer (2 minutes of history at 1 Hz). Buffers are per-server or per-GPU and grow dynamically as new GPUs appear.

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